Molybdenum-base alloy



Sept. 2, 1958 J. D. NISBET 2,850,385

MOLYBDENUM-BASE ALLOY Filed Aug. 29, 1955 s Sheets-Sheet 1 f v v AAA 54 A James D. Nisber ea 60 INVENTOR. 50% 50 4 M 0 IO M 20 3O 4O 50 T1, per cent ATTORIl-TYS.

Sept. 2', 1958 J. D. NISBET 2,850,385

MOLYBDENUM-BASE ALLOY Filed Aug. 29, 1955 5 Sheets-Sheet 5 Avmmmmm vvvwvw V, per cent WW 5 WVVWWW O gmm z vwz s w mo A 0 IO 20 3O 4O 50 V, per cent ATTORNEYS.

United States Patent Patented Sept. 2, 1958 ice MoLYBnnNUM-nAsn ALLOY James D. Nisbet, Pittsburgh, Pa, assignor to Universal- Cyclops Steel Corporation, Bridgeville, Pa, a corporation of Pennsylvania Application August 29, 1955, Serial No. 531,056

6 Claims. (Cl. 75-176) Thisinvention relates to molybdenum-base alloys, and more" specifically to molybdenum-base alloys which exhibit superior strength and hardness over a wide range of temperatures.

For a great variety of industrial and military applications, itis highly desirable to use metals that maintain their hardness and strength at elevated temperatures. For such applications as gas turbine components, jet engine parts, high-speed cutting tools and dies there is an ever-increasing demand for hard and strong metals and materials that will retain such hardness and strength at higher temperatures.

Although the alloys used today, such as the cobaltchromium-nickel alloys for high-temperature, highstrength applications are far superior to metals once'used for high-temperature applications, the increasing demands for harder and stronger metals for high-temperature applications make any advance in the art toward this goal highly significant.

The. principal object of this invention is to provide improved cast alloys which exhibit high strength and hardness at both room and elevated temperatures.

Another object of this invention is to provide molybdenum-base alloys which retain high hardness at elevated temperatures.

Another object of this invention is to provide molybdenum-base alloys which will retain room-temperature hardness properties after being subjected to high temperatures.

Other objects and advantageous features will be obvious in the following specification and examples.

In. accordance with the present invention binary, ternary and complex molybdenum-base alloys have been found that. possess improved strength properties at ele vated temperatures.

in general, this invention relates to molybdenum-base alloys containing at least one metal selected from the high-melting-pointrefractory metals from the lV-A, V-A, and VI:A atomic groups of the periodic table. Specifically, this invention relates to' hard, high-melting-point alloys which possess high strength or hardness at room and elevated temperatures and which contain at least 50 percent molybdenum and at least one'metal selected from.

the group tantalum, titanium, columbium, vanadium, tungsten, and chromium.

In thedrawings:

Fig. 1- is atriaxial diagram on which is plotted com-- positions of molybdenum-base alloys containing vanadiumv and/or titanium as in Fig. 1 but the- Vickers hardness numbersof Fig. 2 are taken at 700 C.

Fig. 3 is a triaxial diagram on which are plotted compositions of molybdenum-base alloys containing vanadium.

2 and/or titanium as in Fig. l but the Vickers hardness numbers of Fig. 3 are taken at 900 C.

Fig. 4 is a triaxial diagram on which is plotted compositions and hardness levels of binary and ternary molybdenum-base alloys containing chromium and/or titanium. The hardnesses are room temperature Vickers hardness numbers.

Fig. 5 is a triaxial diagram on which are plotted compositions of molybdenum-base alloys containing chromium and/or titanium as in Fig. 4 but the Vickers hardness numbers of Fig. 5 are taken at 700 C.

Fig. 6 is a triaxial diagram on which are plotted compositions of molybdenum-base alloys containing chromium and/or titanium as in Fig. 4 but the Vickers hardness numbers of Fig. 6 are taken at 900 C.

Fig. 7 is a triaxial diagram on which is plotted compositions and hardness levels of binary and ternary molybdenunmbase alloys containing chromium and/or vanadium. The hardnesses are room-temperature Vickers hardness numbers.

Fig. 8 is a triaxial diagram on which are plotted compositions of molybdenum-base alloys containing chromium and/or vanadium as in Fig. '7 but the Vickers hardness numbers of Fig. 8 are taken at 700 C.

Fig. 9 is a triaxial diagram on which are plotted compositions of molybdenum-base alloys containing chromium and/ or vanadium as in Fig. 7 but the Vickers hardness numbers of Fig. 9 are taken at 900 C.

In the drawings, the top or uppermost point of the triaxial diagram represents percent molybdenum, while the base of the diagram represents 50 percent molybdenum. Alloying metals are designated for each side of the diagrams. The composition of any point on the diagram may be determined by reading molybdenum content from the bottom to the top at 10 percent intervals, as indicated. Alloying metal contents are determined by projecting a line from the point to the side of the diagram representing such addition, parallel to the lines projecting beyond the diagram and read at 10 percent intervals, as indicated. For example, in Fig. 1 titanium content is determined by projecting a line to the bottom of the diagram, as indicated, parallel to the lines extending slightly below the diagram at the bottom and read from left to right. Vanadium content is determined in the same manner as the titanium content but read along the left side of the diagram, as indicated. The points which are marked and Vickers hardness numbers given are actual examples produced in the laboratory and charted on the diagrams. The solid lines are contour lines designating levels of hardness and the circled numbers indicate the hardness levels by Vickers hardness numbers.

Molybdenum-base binary alloys, containing as the alloying addition, titanium, vanadium, chromium, columbium ortantalum have beenfound to have excellent high-strength or' hardness properties at both room temperature and at'elevated' temperatures. In a like manner, ternary alloys containing at least 50 percent molybdenum and at least two metals selected from the group titanium, vanadium, chromium, tungsten, columbium, and tantalum have been found to have equal or superior strength to the binary system.

Alloys which are suitable for applications such as highspeed cutting tools, dies, jet engine parts, and gas-turbine components preferably have a room-temperature hardness of' at least 300 Vickers hardness number and for hightemperature applications a hardness of at least Vickers hardness number. Table I below illustrates the mini.- mum binary alloying additions to molybdenum which will result in minimum room-temperature hardnesses of at last 300 Vickers hardness number and at least 150 Vickers hardnessnumber at a temperature of 700 C.

It is further illustrated by Figs. 1 through 9 and Table II that ternary alloys containing at least 50 percent molybdenum and at least one of any of the above binary additions to molybdenum will present high strength properties.

The properties of three of the binary and three of the ternary alloys are clearly illustrated in Figs. 1 through 9.

The range of molybdenum-titanium-vanadium alloys possessing room-temperature hardnesses in excess of 300 Vickers hardness number and 150 Vickers hardness number at'7 C. are clearly illustrated in Table II and Figs. 1 and 2. These ternary alloy compositions are shown in Fig. 2 by all of the compositions falling below the 150 Vickers hardness number level. The range of molybdenum titanium chromium alloys possessing roomtemperature hardnesses in excess of 300 Vickers hardness number and 150 Vickers hardness number at 700 C. are clearly illustrated in Figs. 4 and 5. These ternary alloy compositions are shown in Pig. 5 by all the compositions falling below the 150 Vickers hardness number level. The range of molybdenum-vanadium-chromium alloys possessing room-temperature hardnesses in excess of 300 Vickers hardness number and 150 Vickers hardness number at 700 C. are clearly illustrated in Figs. 7 and 8. These ternary alloy compositions are shown in Fig. 8 by all the compositions falling below the 150 Vickers hardness number level line.

In a similar manner, ternary alloys including at least two of the binary additions described above will provide room-temperature hardnesses in excess of 300 Vickers hardness number and high-temperature properties of at least 150 Vickers hardness number at 700 C.

Alloys containing more than 50 percent alloying additions to molybdenum are outside the range of the alloys disclosed and are no longer molybdenum-base alloys. Strength properties generally fall off as the alloying content increases beyond 50 percent. The molybdenum content is, therefore, preferably a minimum of 50 percent by weight of the alloy.

Tungsten may be alloyed to molybdenum as a ternary or complex alloying addition falling within the scope of the present invention, so long as the strength properties at room and elevated temperatures are not adversely affected. For examples, as may be noted by referring to,

Table II, binary molybdenum-tugsten alloys possess hardnesses far below 150 Vickers hardness number at a temperature of 700 C., therefore, binary molybdenumtungsten alloys do not fall in the scope of the present invention. Also, as exemplified by Table II, ternary molybdenum-tungsten alloys may possess sufiicient hardness properties to fall Within the scope of the present invention. However, the alloys of the present invention contain at least 50 percent molybdenum. As can be seen in Table 11, large additions of tungsten may be made while retaining high hardness.

It can be seen from Figs. 3, 6, and 9 that there are also optimum ranges for certain molybdenum-base ternary alloys. These alloys exhibit a minimum of hardness of 250 Vickers hardness number at 900 C. Though the alloys of this invention retain, to a remarkable extent, their hardness at elevated temperatures, there is, of course, some hardness drop-off as the temperature rises. Although hardnesses of 150 Vickers at temperatures as high as 700 C. are useful high-temperature properties, it is felt that hardnesses of 250 Vickers at temperatures of 900 C. are of much greater significance. Such hightemperature hardness and strength render these alloys. within the optimum composition ranges, ideal materials for high-temperature applications where high-strength properties are required. Compositions exhibiting 250 Vickers or greater hardness at 900 C. are set forth in Figs. 3, 6, and 9 of the accompanying diagrams Within the 250 Vickers hardness number levels.

Microscopic studies show that molybdenum-base alloys containing titanium, vanadium, tantalum, columbium, chromium and tungsten are all single phase solid solution alloys. The alloys discussed so far are, therefore, the solid solution type of alloys which exhibit solid solution strength properties.

It has been found that improved room and elevated temperature strength properties may be attained by alloying zirconium with the other molybdenum-base alloys of the present invention. 7 The addition of zirconium to molybdenum or molybdenum-base alloys results in microscopic structures composed of a terminal solid-solution phase of zirconium in molybdenum and the intermetallic compound ZrMo The difliculty experienced with this type of alloy is the complete lack of workability of the metal at either room or elevated temperatures, however, it has been found that small additions of zirconium to the above binary or complex alloys may be satisfactorily employed to attain improved strength properties while retaining the required degree of workability necessary to be adapted to high-temperature applications. The small additions of zirconium to the terminal solid-solution phase molybdenum-base alloys which may be employed to atgiven in Table II illustrate the extreme hardness of the.

binary alloy.

It is obvious that combinations including any of the alloying additions to molybdenum of this invention can be made to form alloys containing three and even four alloying elements, without departing from the scope of this invention.

The molybdenum-base alloys of the present invention were arc-melted using a water-cooled hearth. A very pure helium atmosphere at low pressures (10 to 20 cm. of mercury pressure) was employed. By using a pure helium atmosphere, little or no oxygen pickup was experienced so that it was not necessary to add deoxidants such as carbon, aluminum, or boron to the melts. It should be noted that additions of such elements as carbon, aluminum, or boron generally harden the metal to some extent.

Table II below covers all the ranges disclosed above, illustrates specific examples of the molybdenum-base alloys of this invention and shows their strength properties at various elevated temperatures.

Table II Vickers hardness number Composition, weight percent (balance Mo) Mo (unalloyed) 180 74 60 47 2.5 1. 1" 225 232 279 211 96 170 404 292 242 239 203 397 288 250 231 234 370 303 254 242 242 316 .236 225 201 205 208 208 251 178 151 144 149 336 248 197 199 194 384 257 228 211 198 378 268 239 217 212 370 222 228 202 199 203 296 305 202 165 140 336 260 231 208 187 549 462 375 337 273 613 506 412 337 299 418 389 380 307 Table II.-Continued Composition, weight percent (balance M0) Vickers hardness number 25 C. 300 0. 500 C. 700 C. 900 C 220 269 173 154 132 134 324 218 198 174 167 .397 265 233 211 431 275 267 250 250 476 284 286 278 267 207 206 231 137 107 96 108 302 191 181 150 168 343 259 220 199 220 396 275 244 242 234 459 286 253 223 234 451 284 256 229 235 440 315 282 270 235 459 250 233 216 239 417 497 380 387 432 322 299 259 254 424 234 218 201 185 439 390 270 235 220 254 508 357 352 297 315 601 379 329 311 288 475 286 277 275 248 Ti-30 Or 599 40 Ti-10 Cr 426 297 259 262 236 10 Ti-40 Cr 649 20 Ti-20 Cr 503 383 379 405 329 20 Ti-30 C1' 570 379 379 322 277 30 Ti-20 C1: 577 370 383 263 284 10 Cr-IO V- 384 247 248 221 214 20 Cr-lO V 696 437 398 380 337 10 Cr-20 V 428 247 190 226 182 40 Cr-10 V- 613 288 250 322 270 10 CF40 V 429 290 271 263 221 30 Cr-20 V- 693 20 (Jr-30 V 693 516 456 396 376 25 Cr-25 Cb 645 25 Or25 Ta.-- 371 25 (Jr-25 Ti 424 25 013-25 Ta 435 25 011-25 Ti 414 25 (lb-25 W 393 25 Ta-25 TL 425 25 Ta-25 V 473 25 Til-25 W"- 361 25 Ti-25 W 427 25 V-25 W- 372 What is claimed is:

1. An alloy consisting essentially of at least 50 percent molybdenum, and two metals selected from the group consisting of 10 to percent tungsten, 10 to 40 percent titanium, 10 to 40 percent vanadium, 10 to 40 percent chromium, 10 to 40 percent columbium, and 10 to 40 percent tantalum, and characterized by high strength properties.

2. Alloys consisting essentially of at least percent molybdenum, from 10 to 40 percent titanium, from 10 to 40 percent vanadium, and characterized by higher strength properties than binary molybdenum-titanium and molybdenurn-vanaclium alloys.

3. Alloys consisting essentially of at least 50 percent molybdenum, from 10 to 40 percent titanium, and from 10 to 40 percent chromium.

4. Alloys consisting essentially of at least 50 percent molybdenum, from 10 to 40 percent chromium, and from 10 to 40 percent vanadium.

5. Alloys consisting essentially of at least 50 percent molybdenum, from 10 to 40 percent chromium, and from 10 to 40 percent tantalum.

6. Alloys consisting essentially of at least 50 percent molybdenum, from 10 to 40 percent chromium, and from 10 to 40 percent tungsten.

References Cited in the file of this patent UNITED STATES PATENTS 1,881,315 Honda et a1. Oct. 4, 1932 2,678,268 Ham et a1 May 11, 1954 2,678,269 Ham et a1. May 11, 1954 2,678,270 Ham et al May 11, 1954 2,678,271 Ham et a1. May 11, 1954 2,678,272 Ham et al. May 11, 1954 OTHER REFERENCES ASM Preprint No. 33, paper presented 31st Annual Convention of the ASM, Cleveland, Ohio, Oct. 17-21, 1949, received in Patent Off. Sept. 26, 1949. A Study of Arc Melted Molybdenum-Rich Chromium Molybdenum Alloys, Kessler et al. 

1. AN ALLOY CONSISTING ESSSENTIALLY OF AT LEAST 50 PERCENT MOLYBDENUM, AND TWO METALS SELECTED FROM THE GROUP CONSISTING OF 10 TO 40 PERCENT TUNGSTEN, 10 TO 40 PERCENT TITANIUM, 10 TO 40 PERCENT VANADIUM, 10 TO 40 PERCENT CHROMIUM, 10 TO 40 PERCENT COLUMBIUM, AND 10 TO 40 PERCENT TANTALUM, AND CHARACTERIZED BY HIGH STRENGTH PROPERTIES. 